This invention relates to a method of forming a package from a wrapper sleeve which is of a heat-sealable material and which is provided with a longitudinal seam as well as fin seals at opposite longitudinal ends.
According to conventional package making methods, wrapper sleeve packages, particularly for chocolate bars are formed by wrapping the mutually spacedly delivered bars with a continuous wrapper and providing the wrapper with a longitudinal seam to thus obtain a wrapper sleeve. After laying flat the longitudinal seam onto the underside of the package, the wrapper sleeve is pressed flat between two adjoining bars, sealed and then severed, whereby at both ends of each package a fin seal is provided. Such packages can be manufactured inexpensively and with high output. The required machinery thus needs only simple sealing shoes and low sealing temperatures because the sealing seam is of the single-layer type.
It is a disadvantage of the package made as outlined above that the width of the fin seals is substantial, thus lending the package an inferior appearance. For this reason, such a package is rarely used, if at all, for wrapping high-quality products. Further, such large-dimension fins require substantial space which is an added disadvantage in boxed packaging, display racks or vending machines.
For the above reasons, aesthetically more pleasing packages are made with pinch folds provided at the longitudinal package ends as described, for example, in U.K. Pat. No. 679,052. According to such a method, at the ends of the package, at two opposite narrow sides, a pinch fold is formed prior to pressing the sleeve flat. Subsequent to such pressing and sealing, the transverse seam at the two ends of the package does not exceed the width of the wrapped product. Consequently, it may be folded down onto the end faces of the package and glued thereto. Due to the structure of the pinch fold, the end seam is partly single-layered, partly dual-layered. For this reason difficulties are encountered in obtaining satisfactory sealing properties. Higher sealing temperatures have to be used to ensure that a proper seal is provided at the dual-layered zone as well. This, however, involves the problem that the sealing temperature will be too high for the single-layered zone and therefore longer cooling periods have to be provided. Consequently, these packages cannot be produced with an output as high as that for the fin-seal packages outlined earlier.
A further wrapper sleeve package with pinch fold is disclosed in Swiss Pat. No. 254,978. In this case too, the seam at the ends of the package is single-layered in part and double-layered in part so that the same problems are encountered as concerns seal quality and output as in the arrangement according to the earlier-described U.K. Pat. No. 679,052. In addition, in the package the flap of the lateral end closure is folded onto that large surface which is free from the longitudinal seam. Consequently, the two large faces of the bar can only be used with difficulty, if at all, as display surfaces so that such packages conventionally have to be provided with a second wrapper, representing additional expense.